Historically, the electric drive industry has been relatively slow to adopt changes relating to controlling and/or powering end devices, such as motors. Typically, if a computer is involved in controlling the operation of a motor, a programmable logic controller (PLC) is usually utilized to control the computer within the motor controller, if used, via a standard physical communications layer. In addition, various types of sensors, e.g., temperature, pressure, etc., may be "hard-wired" to the PLC resulting in a substantial investment in cabling. In many instances a plurality of computers within electrical devices and their associated PLC's may be interconnected into a network, typically in a master-slave arrangement, resulting in a very complex system and substantial cost to "hard-wire" same. The end result is a system or network that is costly to install and difficult to reconfigure or alter with respect to functionality. In addition, the controller utilizes a substantial amount of hardware, such as gates, etc., (hereinafter referred to as intervening combinational logic devices) to condition the signals produced by the computer prior to applying same to the power switching devices associated with the end device. Such hardware makes it difficult to modify the system so as to be able to utilize power switching devices having different characteristics.
For example, if the end device is an AC motor, and a computer is used in the motor controller (sometimes called an inverter) to vary the speed of the motor, there will be logic gates and/or devices between the computer and the power switches (such as Integrated Gate Bipolar Resistors, IGBTs). Logic devices modify the signal(s) issued by the computer to ensure that the signal accomplishes the desired task and that a dead short does not occur between the switches. Because these switches turn off and on thousands of times per second, sometimes these logic gates are complex and are contained in an Application Specific Integrated Circuit (ASIC). The software within the computer must work to initiate the appropriate signals that make the intervening combinational logic devices operate the specific power switches properly. This combination of hardware and software therefore has the functionality of making the speed of an AC motor variable. But, even though the software in the computer could possibly be altered, the combination of hardware and software has now become fixed. If a radical new kind of power switch comes on the market or a switch with new characteristics is developed both the intervening hardware and possibly the software in the microcomputer will have to be altered for the motor controller to use the new power switching devices.
The lack of flexibility in the above mentioned motor controller is also apparent in the industrial automated systems in which it is used. Frequently the PLC will have hardware and software that will allow it to interact with the specific motor controller listed. Complexities of combining the different hardware and software combinations needed to accomplish even a relatively simple system of a few motors, motor controllers and sensors and a corresponding PLC lead many industrial systems integrators to use only products made by one company in their design in hopes that they will be able to get the overall system to work. Because the hardware/software co-dependency is so high in many high power industrial products changing even a few products can send a project into major redesign.
In view of the foregoing problems associated with the prior art approach to electrical power and control systems, it has become desirable to develop electrical apparatus utilizing a computer to control the operation of an end device without any intervening combinational logic devices to condition the signals produced by the computer prior to applying same to the power switching devices associated with the end device, and wherein the resulting apparatus can be interconnected in a peer-to-peer network.